Radio-frequency transmission device



5 Y RTU www/W M EL VR 0 MEM? w Nv M0. A M Y m. me. or D5 Y B mm. whgwwwLbn D. H. PREIST ETAL RADIO-FREQUENCY TRANSMISSION DEVICE June 9, 1953Filed April 18, 1949 June 9, 1953 D. H. PREIS-r ETAL RADIO-FREQUENCYTRANSMISSION DEVICE 2 Sheets-Sheet 2 Filed April 18, 1949 INVENTOR`DONALD H. PQE/57' Brno/v 0. ALLoU ATTORNEY Patented June 9, 1953RADIO-FREQUENCY TRANSMISSION DEVICE Donald H. Preist, Tiburon, and ByronOf. Ballou,

San Bruno, Calif., assignors to Eitel-McCullough, Inc., San Bruno,Calif., a corporation of California Application April 18, 1949, Serial No. 88,182

2 Claims.

Our invention relates to generators of radiofrequency power, and moreparticularly to such a generator capable of delivering large orders ofpower in the higher frequency ranges, say above 100 mcs/sec., usingconventional type negat1ve grid tubes.

In the copending application of Donald H. Preist, Serial No. 42,171,filed August 3, 1948, now Patent No. 2,554,500, issued May 29, 1951,there is disclosed a new type of R. F. generator embodying an annularcavity resonator operating in conjunction with a plurality of tubeunits, whereby the power outputs of the individual tube units arecombined without appreciable loss,

'Ihe object of our present invention is to provide an improvedconstruction for such a multiple unit tube generator.

The invention possesses other objects and features of advantage, some ofwhich with the foregoing, will be set forth in the following descriptionof our invention. It is to be understood that we do not limit ourselvesto this disclosure of species of our invention, as we may adopt variantembodiments thereof within the scope of the claims.

Referring to the drawings:

Figure 1 is a vertical sectional view of a power amplifier embodying theimprovements of our invention; and

Figure 2 is a plan view of the same, the line I-I indicating the planeof section of Figure 1.

In terms of broad inclusion, the radio-frequency generator of ourinvention comprises a plurality of tube units disposed in -a circleabout an axis, and a pair of annular cavity resonators l coaxial withthe circle and having conductors connected to electrodes of the tubeunits, each resonator comprising two communicating annular cavitysections. As embodied in an amplifier one of these cavity resonatorsfunctions as the input circuit and the other as the output circuit. Inour generator of such annular construction improved means are providedfor feeding R. F.

power into and out of the resonators. The output transmission linecoupled to the output resonator is arranged coaxially with thegenerator, and the input transmission line coupled to the inputresonator is spaced from the generator axis, a plurality of the inputlines being provided and so spaced as to lie in the circle defined bythe tube units. An output tuning stub is also preferably provided,formed as an extension of the output line and located centrally of thegenerator.

In greater detail, and referring to the drawings, our improved R. F'.generator constructed as an amplifier comprises a plurality of electrontube units I disposed in a circle about a common axis, which tube unitsare of like structure and have like characteristics. While four tubeunits are shown, it is understood that any desired number may beemployed, depending upon the power output required. Any conventionaltype of negative grid electron tube may be used for the units I, thetriode type of tube illustrated having a cathode 2, grid 3 and anode 4,the anode being external and all the electrodes being preferablycylindrical and coaxial.

The tube units employed `also preferably have coaxial terminals for theelectrodes, such as the cathode terminal 6 opposite the anode and thegrid terminal ring 'I interposed in the glass envelope wall between thecathode terminal and anode. The heating structure for the cathode is notshown but may comprise any suitable means such as an inner filament forheating the cathode cylinder 2 by electron bombardment, in which casethe filament leads preferably extend out through the tubular cathodeterminal 6.

The amplier has a pair of annular cavity resonators common to the tubeunits I, functioning as the input and output resonant circuits for suchunits. Each resonator has two communicating annular cavity sectionsarranged coaxially with the circle of tube units, thus the inputresonator has the two annular cavity sections 8 and 9 communicatingthrough spaces between the lower portions of the tube units, and theoutput resonator has the two annular cavity sections I I and I2communicating through spaces between the upper portions of the tubeunits. This symmetrical arrangement of the cavity resonators withrespect to the tube units is an important feature in our R. F.generator.

The two cavity sections 8 and 9 of the input resonator extend downwardlyfrom a plane defined by the circle of tube units, say a plane passingthrough the mid-portions of the units I. Cavity sections I l and I2 ofthe output resonator also extend downwardly from such plane and surroundthe input resonator.

The several cavity sections of the resonators are denned by metallicboundary walls or conductors which make up the physical structure yofthe amplier. As illustrated, the annular cavity sections of theresonators are defined by six concentric wall conductors I3, I4, I6,I'I, I8 and I9. The shorter walls are connected across the top by ametal ring 20, these parts comprising an inner conductor of the inputresonator. I'his inner conductor is connected to the cathode 2 of eachof the tube units, preferably by having cathode terminals 6 seated inapertures or sockets in the lring 20.

Suitable leads for the cathode heater means may conveniently extend outthrough the hollow space formed between the walls I3 and I4.

A transverse conductor member or metal ring 2| extends across the top4of the input resonator in the plane of the grid terminal rings 'I andis connected .to the vcylinders I6 and l1. .This .transverse conductorcomprises the top Wall of the input cavity 8-9 and also forms a commondividing wall between the input and output resonators. v

Cavity sections 8 and 9 of theinput resonator .are thus connected abouttheir circumference by the communicating space formed between thetransverse wall members 2D and 2I. Conductor 2| is electricallyconnected for R.. F. to the grid V3 of each of the tube units throughsuitable bypass condensers as hereinafter described.

Wall conductors I8 and I9 are joined across the top by a transverse wallconductor 2e. Cavity. sections lI and I2 of the output resonator arethus .also ycorn'iected about their circumference by the communicatingspace formed between .the 'transverse'wallrneinbers 2l and-24. Conductor.2lI1is electrically connected ,for R. F. to the vanode Azoffeach'of thetube units'through suitable bypass condensersas hereinafter described.

By this :arrangement it will be seen that 'the cavity resonators are`coaxial with the circle vor tube units, and are disposed in such amanner that the `tube units arelocated between the Yannular cavitysections of the resonators, with the cathodes connected to .a conductorof the input resonator, the anodes connected to a conductor of theoutput resonator and thegrids connected to a common transverse conductor'between the resonators.

It will thus'be noted .that each resonator cornprises v'two cavitysections, each section being constitutedby the space between a pair ofconcentric cylinders. The lengthof each'section, 'measured a yaxially ofthe circle of tube units, is substantially greater than the width of thesection, measured radially of the circle of tube units, i. e., thedifference in radius of the concentric cylinders which Vdeiine thesection (ignoring the thickness of the cylinders). An annulus having agreater 4axial than radial dimension, measured as described, is definedhereinafter as an axially ex-` tending annulus.

The 'several cylindrical conductors of the resonators are heldmechanically in position by rings 2.8, 2S, -30 and 3I of suitableinsulating material located between the conductors at the bottom of @thegenerator. Any suitable metal such as brass maybe used for the variouscylindrical and transverse conductors described.

Adjustable means are provided for tuning the input and output resonatorsto the desired resonant frequency. For thispurpose a pair of mov- .ableannular metal plungers or shorting bars 32 and 33 are provided intheinput resonator, `forming end walls in the cavity sections and 9respectively. vThese plungers are slideably mounted on the wallconductors, and axial adjustment is achieved by means of .plunger rods34 and 35 of insulating material projecting out through the supportsgand 30. These rodsmay be connected externally to insure that theplungers are adjusted in unison.

.In a like manner plungers St and 39 are providedin the cavity sectionsI I and l2 of the `output resonator, which plungers are slideablymounted on the wall conductors and adjusted by plunger rods lll ande?.

The D. C. voltages may be applied to the tube electrodes in any suitablemanner. In the amplifier illustrated, which is essentially agrid-separation type of circuit, the positive D. C. anode potential andbias voltages are applied through suitable leads to the anodes and gridterminal rings. Suitable leadsvfor the cathode heaters for `the severaltube units are conveniently brought out through the hollow space betweenthe conductors I3 and Ill.

The D. C. voltages are preferably isolated by suitable .bypasscondensers at the anode and grid terminals of the tube units. Forexample, each anode fi is preferably provided with a terminal disk 46located below the anode cooler lil; the latter being either of a nnedtype as illustrated for forced air Acooling or of the jacket type forwater cooling. The bypass condenser is conveniently formed by rings I ofinsulating material separating the terminal disk 4e from the conductor2d at one side and a retaining ring i9 on the .opposite side. In a likemanner a terminal disk 5I is connected to the grid terminal ring 'I andseparated from :the 'conductor 2| and a retaining ring 52 by .rings 53of insulating material. For convenience of replacing the tubes, the gridterminal disk 5I preferably has contact iingers 54 for yengaging thegrid ring I so that the tube-plugs ,into .this part as a socket, wherebythe tube may lbe withdrawn by merely removing the retaining ring 49 orhaving a suitable joint in the terminal disk 46.

An important feature of our present invention Ais themeans .employed fortransferring and coupling R. F. power into and out of vanannulargenerator of the .character described. Driving power from a suitablesource tothe input resonator is transferred by a coaxial transmissionline '5t extending up through the open space between conductors I3 andIH. and suitably arranged between the tube units I. This line comprisesan inner conductor `5'I terminating at the transverse meinber '2| and anouter conductor 58 `terminating at the transverse member 29, thus.providing the desired coupling for transferring energy from thetransmission line 56 to the input resonator, it being noted that theinput transmission line 5t terminates at the communicating space betweenthe cavity sections 8 and 9. At least two of the input lines 56 arepreferably incorporated, diamet-rically disposed as illustrated inFigure 2, so Ias lto .provide a balanced coupling. These lines arepreferably connected externally to a common transmission line (notshown) which feeds the power from the driving source. In other words,

'the 'input transmission lines 55 are spaced from the'axis of thegenerator and lie in the same circle as the tube units l. The advantageof this oir"- center arrangement of the input lines is that it providesa satisfactory means for coupling the driving power into the annularinput resonator without taking up space along the axis of the generator,which central space may be then utilized for other purposes.

Power is preferably transferred from the output resonator by .atransmission line E5) along the axis of the generator, and comprising an.outer conductor 5I terminating at the transverse conductor 24 and aninner conductor E52 extending downwardly within the conductory I8.Coupling of energy from the output resonator is established by thecircular slot 53 formed between the ends of aligned conductors 6l andI8. The extension of the inner conductor @2 together with thesurrounding conductor IB provides an output tuning stub which is tunedby an annular snorting bar 64 adjusted by plunger rods 66. Thisarrangement of the input and output transmission lines and the outputtuning stub provides a very compact generator construction.

In our improved R. F. generator the overall diameter of the generatormay be increased indefinitely to accommodate an indenite number of tubeunits, depending upon the amount of power required. Furthermore, themultiple unit tube generator described will operate well in the higherfrequency ranges, say above 500 mcs/sec., without loss of efficiencycompared to that obtainable from a single tube unit. The total poweroutput from n tube units, as measured at the load, is substantially ntimes that obtainable from a single tube unit in an efcient single unittube generator.

While we have described our generator in connection with triode units,it is understood that tube units having additional electrodes such astetrodes may be emploged, in which case additional annular, coaxial andsymmetrical circuit members are employed.

We claim:

1. A radio-frequency transmission device comprising a plurality ofelectron tube units disposed in a circle about an axis and each havingrelectrodes including an anode and cath-ode, an output cavity resonatorcommon to the tube units and having two communicating, axiallyextending, annular cavity sections, the output resonator being coaxialwith said circle and having a conductor connected to an anode of each ofthe tube units, an input cavity resonator common to the tube units andhaving two communicating, axially extending, annular cavity sections,the input resonator being coaxial with said circle and having aconductor connected to a cathode of each of said tube units, the axialdimension of each cavity being substantially greater than the radialdimension thereof, an output transmission line coaxial with said circleand coupled to the output resonator, a tuning stub coaxial with saidcircle and forming an extension of the output line, and an inputtransmission line spaced from said axis and coupled to the inputresonator.

2. A radio-frequency transmission device comprising a plurality ofelectron tube units disposed in a circle about an axis and each havingelectrodes including an an-ode and cathode, an output cavity resonatorcommon to the tube units and having two communicating, axiallyextending, annular cavity sections, the output resonator being coaxialwith said circle and having a conductor connected to an anode of each ofthe tube units, an input cavity resonator common to the tube units andhaving two communicating, axially extending, annular cavity sections,the input resonator being coaxial with said circle and having aconductor connected to a cathode of each of said tube units, the axialdimension of each cavity being substantially greater than the radialdimension thereof, an output transmission line coaxial with said circleand coupled to the output resonator by a circular slot, and a tuningstub coaxial with said circle and forming an extension of the outputline on the opposite side of said slot.

DONALD H. PREIST. BYRON O. BALLOU.

References Cited in the ile of this patent UNITED STATES PATENTS NumberName Date 2,173,908 Kolster Sept. 26, 1939 2,281,550 Barrow May 5, 19422,284,405 McArthur May 26, 1942 2,363,641 Carlson Nov. 28, 19442,404,261 Whinnery July 16, 1946 2,407,068 Fiske et al. Sept. 3, 19462,412,805 Ford Dec. 17, 1946 2,554,501 Preist May 29, 1951 2,554,502Prest May 29, 1951

